Optical measurement systems and processes with fixation target having bokeh compensation

ABSTRACT

A system includes: at least one processor; a movable stage, wherein the movable stage is movable under control of the at least one processor with respect to an eye of a subject; a video display device configured to move with the movable stage; and an optical system disposed in an optical path between the video display device and the eye. The video display device is configured to play a movie of a fixation target to the eye to cause the eye to accommodate, and the movie dynamically changes an appearance of the fixation target on the video display device to compensate for Bokeh of the fixation target as the movable stage moves the video display device from a first position, where the fixation target draws a focus of the eye to near its far point, to a second position further away from the eye than the first position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application No. 62/955,271, filed Dec. 30, 2019,which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of this invention pertain to optical measurement equipment,and more particularly, to optical measurement systems and processeswhich include fixation targets for causing a subject's eye toaccommodate during measurement.

BACKGROUND

Autorefractors and aberrometers (e.g., wavefront aberrometers) measurethe refraction of a subject's eye using infrared light. It is desirablethat the eye relax accommodation while the refraction is being measuredto avoid an unknown change in the eye's focal power during themeasurement which can lead to errors or inaccuracy in the measuredrefraction. Accordingly, autorefractors and aberrometers typicallyemploy a fixation target for a person to view while the refractive stateof the eye is being measured. One purpose of the fixation target is todraw the focus of the eye to its most distant refractive state, and thenbeyond, to so-call “fog” the eye while the refraction is being measured.Under these conditions, the eye attempts to keep the target in focus byrelaxing accommodation, which as noted above is desirable. A patient'smost distant refraction is also used for planning refractive eyesurgeries.

However, with conventional autorefractors and aberrometers, about tenpercent of people do not fully relax accommodation in response to thepresented target. Because autorefractors are not completely reliable infully relaxing the accommodation of a significant percentage ofpatients' eyes, the resulting refraction measurements are oftenerroneous or inaccurate. Furthermore, because it is not known whetherthis issue has occurred or not with a particular patient, there is alack of confidence or trust in the results for all patients. Experimentswhere eye glasses have been prescribed based on autorefractions alonehave resulted in a high fraction of unhappy patients. This leadsoptometrists to prescribe eye glasses based on manifest refractionsmeasured with a phoropter instead of using results produced by anautorefractor or aberrometer.

Accordingly, it would be desirable to provide a fixation target systemwhich is more effective in drawing out the eye's refractive state andstimulating fully relaxed accommodation for a greater percentage ofpatients during refraction measurements with an autorefractor oraberrometer. It would also be desirable to provide an opticalmeasurement instrument, such as an autorefractor or aberrometer, whichincludes such a fixation target system. It would be further desirable toprovide an improved method of drawing out the eye's refractive state toproduce fully relaxed accommodation for a greater percentage ofpatients.

SUMMARY OF THE INVENTION

In one aspect, a system comprises: a wavefront aberrometer configured tomeasure a refraction of an eye; at least one processor; a video displaydevice; and an optical system disposed in an optical path between thevideo display device and the eye, wherein the video display presents afixation target to the eye to cause the eye to accommodate during aprocess of measuring the refraction of the eye, and wherein the at leastone processor is configured to dynamically change the fixation target onthe video display device to compensate for Bokeh of the fixation targetas the video display device is moved from a first position, where thefixation target draws a focus of the eye to near its far point, to asecond position which is further away from the eye than the firstposition.

In some embodiments, the at least one processor is configured to movethe fixation target with respect to the eye.

In some embodiments, the system further comprises a first movable stage,wherein the first movable stage is movable with respect to the eye undercontrol of the at least one processor.

In some embodiments, the system further comprises a second movable stagedisposed on the first movable stage, wherein the video display device isdisposed on the second movable stage, wherein the second movable stageis independently movable with respect to the first movable stage andwith respect to the eye, under control of the at least one processor.

In some embodiments, a size of the fixation target on the video displaydevice remains substantially constant as the video display device ismoved further away from the eye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the processor is configured to control thevideo display device to dynamically reduce a thickness of the horizontalline and a thickness of the vertical line as the video display device ismoved further away from the eye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the processor is configured to control thevideo display device to cause each of the horizontal line and thevertical line to have a dynamically increasing taper down to theintersection as the video display device is moved further away from theeye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the processor is configured to control thevideo display device to dynamically decrease an intensity of the crossat a region about the intersection as the video display device is movedfurther away from the eye.

In another aspect, a method comprises: providing an arrangementcomprising: a wavefront aberrometer configured to measure a refractionof an eye; at least one processor; a video display device; and anoptical system disposed in an optical path between the video displaydevice and the eye; the video display device presenting a fixationtarget to the eye to cause the eye to accommodate during a process ofmeasuring the refraction of the eye; moving the video display devicewith respect to the eye to a first position where the fixation targetdraws a focus of the eye to near its far point; moving the video displaydevice with respect to the eye to a second position where the videodisplay device is moved away from the eye by an additional amount; anddynamically changing the fixation target on the video display device tocompensate for Bokeh of the fixation target as the video display deviceis moved away from the eye by the additional amount.

In some embodiments, dynamically changing the fixation target on thevideo display device to compensate for Bokeh of the fixation target asthe fixation target is moved away from the eye by the additional amountcomprises playing a movie on the video target.

In some embodiments, the method further comprises: modeling effects ofthe optical system and aberrations of the eye to determine a series ofmodel fogged images of the fixation target on a retina of the eye as afunction of a distance from the video display device to the eye;analyzing the model fogged images to identify features in the modelfogged images which are inconsistent with how the fixation target wouldappear as the video display device moved more distant from the eye whilethe fixation target was viewed directly by the eye; and creating themovie by performing inverse operations on the fixation target accordingto the identified features in the model fogged images to compensate forthe identified features as the function of the distance from the videodisplay device to the eye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the movie dynamically reduces a thicknessof the horizontal line and a thickness of the vertical line as the videodisplay device is moved further away from the eye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the movie causes each of the horizontalline and the vertical line to have a dynamically increasing taper downto the intersection as the video display device is moved further awayfrom the eye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the movie dynamically decreases anintensity of the cross at a region about the intersection as the videodisplay device is moved further away from the eye.

In some embodiments, the method further comprises measuring a refractionof the eye with the first movable stage at the first stage position andthe second stage at the second stage position.

In some embodiments, the method further comprises measuring therefraction of the eye with a wavefront aberrometer having a wavefrontsensor and a telescope, wherein a first lens of the telescope isdisposed on the first stage and a second lens of the telescope is notdisposed on the first stage or the second stage.

In yet another aspect a system comprises: at least one processor; afirst movable stage, wherein the first movable stage is movable undercontrol of the at least one processor with respect to an eye of asubject; a video display device configured to move with the firstmovable stage; and an optical system disposed in an optical path betweenthe video display device and the eye, wherein the video display deviceis configured to play a movie of a fixation target to the eye to causethe eye to accommodate, and wherein the movie dynamically changes anappearance of the fixation target on the video display device tocompensate for Bokeh of the fixation target as the first movable stagemoves the video display device from a first position, where the fixationtarget draws a focus of the eye to near its far point, to a secondposition further away from the eye than the first position.

In some embodiments, the system further comprises a second movable stagedisposed on the first movable stage, wherein the video display device isdisposed on the second movable stage, wherein the second movable stageis independently movable with respect to the first movable stage andwith respect to the eye, under control of the at least one processor.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the processor is configured to control thevideo display device to dynamically reduce a thickness of the horizontalline and a thickness of the vertical line as the video display device ismoved further away from the eye.

In some embodiments, the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the processor is configured to control thevideo display device to cause each of the horizontal line and thevertical line to have a dynamically increasing taper down to theintersection as the video display device is moved further away from theeye.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages will be facilitated by referring to the following detaileddescription that sets forth illustrative embodiments using principles ofthe invention, as well as to the accompanying drawings, in which likenumerals refer to like parts throughout the different views. Like parts,however, do not always have like reference numerals. Further, thedrawings are not drawn to scale, and emphasis has instead been placed onillustrating the principles of the invention. All illustrations areintended to convey concepts, where relative sizes, shapes, and otherdetailed attributes may be illustrated schematically rather thandepicted literally or precisely.

FIG. 1 illustrates an example embodiment of an optical measurementsystem which includes a wavefront aberrometer.

FIG. 2 illustrates an example of a fixation target system.

FIG. 3 illustrates another example of a fixation target system.

FIGS. 4A and 4B illustrate paths of light rays propagating to the retinaof an eye from a target presented by fixation target systems of FIGS. 2and 3 when the target is in a first location with respect to the eye,and then moved further away from the eye.

FIGS. 5A and 5B illustrate images on the retina of the eye produced by atarget of the fixation target systems of FIGS. 2 and 3 when the targetis in a first location with respect to the eye, and then moved furtheraway from the eye.

FIG. 6 illustrates an example of a fixation target system which employsBokeh compensation.

FIG. 7A illustrates an example of a fixation target which may beemployed in the fixation target system of FIG. 6.

FIGS. 7B and 7C illustrate examples of the fixation target of FIG. 7Awith Bokeh compensation applied.

FIG. 8A is a flowchart of one example embodiment of a method ofproducing a fixation target which includes Bokeh compensation.

FIG. 8B is a flowchart of an example embodiment of a method of measuringone or more characteristics of an eye with a wavefront aberrometer.

FIG. 9A illustrates a front perspective view showing an opticalmeasurement system according to many embodiments.

FIG. 9B illustrates a rear perspective view showing an opticalmeasurement system according to many embodiments.

FIG. 9C illustrates a side perspective view showing an opticalmeasurement system according to many embodiments.

FIG. 10 is a block diagram of a system including an optical measurementinstrument, and a position of an eye relative to the system according toone or more embodiments described herein which may be used by theoptical measurement.

FIGS. 11A and 11B illustrate together an assembly illustrating asuitable configuration and integration of an optical coherencetomographer subsystem, a wavefront aberrometer subsystem a cornealtopographer subsystem, an iris imaging subsystem, a fixation targetsubsystem according to a non-limiting embodiment of the presentinvention.

FIG. 12 is a block diagram of an OCT assembly according to manyembodiments of the present invention.

FIG. 13 is a schematic drawing of a human eye.

FIG. 14A illustrates a preferred scanning region for the OCT subsystemaccording to many embodiments of the present invention.

FIG. 14B shows a representative graph of an intensity of an OCT signalof an OCT subsystem according to many embodiments as a function of depthalong the axis defining the axial length of the eye.

FIG. 14C shows a cross-section of an eye obtained by an opticalmeasurement system of the present invention using an OCT subsystemaccording to the present invention

FIG. 15 is a 3-dimensional representation of an anterior portion of aneye obtained using the optical measurement system according to manyembodiments.

FIG. 16 is a flowchart of an example embodiment of a method formeasuring one or more characteristics of an eye, including wavefrontaberrometry, corneal topography and OCT measurements at variouslocations with the eye along the axial length of the eye.

DETAILED DESCRIPTION

Exemplary embodiments of optical measurement systems and methods formeasuring aberrations of an eye to illustrate various aspects andadvantages of these devices and methods are described below. However, itshould be understood that the principles involved in these devices andmethods can be employed in a variety of other contexts, and thereforethe novel devices and method disclosed and claimed here should not beconstrued as being limited to the example embodiments described below.

U.S. Pat. No. 6,550,917, which is incorporated herein by reference,describes an instrument which includes a wavefront aberrometer, inparticular a Shack-Hartmann wavefront aberrometer that provides anadjustable telescope in the forward path from the light source to theeye and in the return path from the eye to the wavefront sensor. Theadjustable telescope employs a moving stage to move one lens of thetelescope with respect to the other, and a feedback arrangement wherebydata from the wavefront sensor is employed to control a motor for themoving stage to move the stage to the desired location where thewavefront sensor sees collimated return light from the eye. The movingstage may be a common linear travel stage with stepper (or servo) motordrives and a position encoder. The position of the moving stage may becalibrated so the stage position corresponds to the refractive power ofthe eye being measured.

FIG. 1 illustrates an embodiment of a measurement instrument employing awavefront sensor. In particular, FIG. 1 illustrates a wavefrontaberrometer 1000 for making wavefront measurements of a subject's eye101. Among other components, wavefront aberrometer 1000 includes a probebeam light source 1010, a wavefront sensor 1020, and other components ona movable stage 1030, at least one processor 1040, memory 1050associated with the at least one processor 1040, and an iris camera1060.

Probe light beam source 1010 may comprise a laser, a laser diode, LED,or a super-luminescent diode (SLD), which may be connected to an opticalfiber. For safety reasons, probe beam light source 1010 may be a pulsedlight source, may be limited to a small power level, and may be outsidethe normal visual detection range, e.g. infrared.

Wavefront sensor 1020 is a Shack-Hartmann wavefront sensor. In otherembodiments, a shearing interferometer or a Moiré deflectometer may beemployed as a wavefront sensor. Wavefront sensor 1020 includes a lensletarray 1022 and a detector array (also known as a “pixel array”) 1024.Wavefront data from detector array 1024 is supplied to processor 1040and associated memory 1050 to execute one or more algorithms todetermine a wavefront of a light beam received from the eye 101.Beneficially, processor 1040 may perform these algorithms in accordancewith instructions stored in memory 1050. The operation of aShack-Hartmann wavefront sensor in a wavefront aberrometer such aswavefront aberrometer 1000 may be understood with reference to U.S. Pat.No. 6,550,917, which is incorporated by reference, and will not berepeated here.

Wavefront aberrometer 1000 includes an optical imaging system comprisinga telescope having a pair of lenses 1163 and 1164, and a dynamic rangelimiting aperture 1165, for example in an optical screening structure.

Processor 1040 controls the operation of wavefront aberrometer 1000 andcan receive image data from wavefront sensor 1020 to measure therefraction of eye 101, including high order aberrations. Processor 1040may also control movement of movable stage 1030, as described in moredetail below. Processor 1040 may include any suitable components, suchas one or more microprocessors, one or more field-programmable gatearray (FPGA), and one or more memory storage devices.

Beneficially, wavefront sensor 1020 operates in conjunction withprocessor 1040 and associated memory 1050 to perform wavefrontmeasurements on eye 101 to measure, inter alia, a refraction of eye 101.

As explained above, it is desirable that eye 101 relax accommodationwhile the refraction is being measured to avoid an unknown change in thefocal power of eye 101 during the measurement which can lead to errorsin the measured refraction. Accordingly, wavefront aberrometer 1000includes a fixation target 1082 which includes a fixation target 1082for a person to view while the refractive state of eye 101 is beingmeasured to draw the focus of eye 101 to its most distant refractivestate, and then beyond, to fog eye 101 while the refraction is beingmeasured.

FIG. 2 illustrates an example of a fixation target system 2000. Fixationtarget system 2000 includes fixation target 1082, a first lens 1083, asecond lens 1084, and a third lens 1085. Fixation target system 2000includes a movable stage 1088 on which second lens 1084, third lens 1085and fixation target 1082 are disposed or mounted. First lens 1083 is notdisposed or mounted on movable stage 1088. In fixation target system2000, eye 101 is located one focal length from first lens 1083.

In fixation target system 2000, the distance between second lens 1084and third lens 1085 is f2+f3, where f2 is the focal length of secondlens 1084 and f3 is the focal length of third lens 1085. This issometimes referred to as a Badal arrangement. In this arrangement, lightrays that reach eye 101 are telecentric when they leave fixation target1082. By definition that means the chief ray is parallel to the opticalaxis at fixation target 1082. The chief ray is defined as the ray thatleaves the edge of fixation target 1082 and ultimately passes throughthe center of the stop of the system, which is the pupil of eye 101.

Movable stage 1088 may be referred to as a Badal stage, and in someembodiments may comprise the movable stage 1030 of wavefront aberrometer1000 of FIG. 1. In particular, it is commonly noted that in a Badalarrangement, fixation target 1082 appears to maintain constant size to aviewer as it moves away from eye 101 toward optical infinity. A keyadvantage of the arrangement is that a simple optical system can providea similar visual appearance to a wide range of patients, from strongmyopes of −20 Diopters through hyperopes up to +20 Diopters.

During a refraction measurement, the at least one processor 1040 movesmovable stage 1088 and thereby moves fixation target 1082 away fromfirst lens 1083 to make fixation target 1082 appear farther away fromeye 101. Eye 101 attempts to keep fixation target 1082 in focus byrelaxing accommodation. In such a system the only cue that the patientor subject receives from eye 101 that fixation target 1082 is movingmore distant from eye 101 is that the image of target 1082 on the retinaof eye 101 becomes blurred.

However, an underlying problem in the fixation target systems 2000 and3000 is that they create a visual experience that contains conflictingcues to a viewer. The brain knows that when something moves fartheraway, the apparent size of it should become smaller. So the constantsize of the image of fixation target 1082 on the retina of eye 101 whichis projected by the Badal arrangement of fixation target system 2000creates conflicting visuals cue to eye 101. In the presence of theseconflicting visual cues, some people's eyes will not relax accommodationcompletely.

However, the situation is actually a bit worse. Fogging or blurringfixation target 1082 actually increases the apparent size of the imageof fixation target 1082 on the retina of eye 101 by a small amount. Theeffect is particularly pronounced for simple geometric targets, likewhite circular patterns on a black background. If we consider the targetsize appearance to be defined by the illuminated region on the retina, aBadal arrangement such as in fixation target system 2000 only maintainsa constant target size for an eye with an infinitely small pupil.

FIG. 3 illustrates another example of a fixation target system 3000.Fixation target system 3000 is similar to fixation target system 2000with the exception that fixation target system 3000 includes a secondmovable stage 1089 on which fixation target 1082 is disposed or mounted,wherein the second movable stage 1089 is disposed or mounted on firstmovable stage 1088. The at least one processor 1040 may independentlymove second movable stage 1089 with respect to first movable stage 1088and eye 101. Second movable stage 1089 may be referred to as a foggingstage as its purpose is to move fixation target 1082 further away fromeye 101 once movable stage 1088 has placed fixation target 1082 near thefar focus point of eye 101, so as to fog eye 101.

First movable stage 1088 has a large range and is used to positionfixation target 1082 in the range for myopes to hyperopes; in someembodiments from −20 Diopter to +20 Diopters. Second movable stage 1089has a smaller motion range to provide an independent fogging motion; insome embodiments of up to 3 Diopters.

As a practical example, consider an exemplary case where the focallengths of lenses 1083, 1084 and 1085 are 73, 45 and 30 mm,respectively. Moving second movable stage 1089 by 4.0 mm under controlof the at least one processor 140 creates a fogging amount on the eye of1.5 diopters. The magnifications calculated using the chief ray wouldindicate the image of fixation target 1082 on the retina of eye 101remained constant when second movable stage 1089 moved. However, if weconsider a reasonable sized eye pupil diameter of 4 mm, the size of theimage of fixation target 1082 on the retina actually increases by 15%due to the blurring effect.

In particular, optical simulations and visual observations of fixationtargets in Badal systems show that distracting features can form in theblurred image that are inconsistent with the fixation target moving moredistantly away from the eye. In the terminology of photography, thisformation of distracting features is described by Japanese term ofBokeh, The study of Bokeh is a relatively recent development inphotographic lenses.

More information about Bokeh may be found, for example, at:https://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-bokeh,and in Wikipedia at https://en.wikipedia.org/wiki/Bokeh. As used herein,the term Bokeh means the way that the lens of an eye rendersout-of-focus points of light when imaging an object (e.g., fixationtarget 1082) on the retina of the eye (e.g., eye 101).

The Zemax analysis diagrams of FIGS. 4A and 4B illustrate the situation.FIGS. 4A and 4B illustrate paths of light rays propagating to the retinaof eye 101 from fixation target 1082 presented by fixation targetsystems 2000 and 3000 when fixation target 1082 is in a first locationwith respect to eye 101, and then moved further away from eye 101. Thecurved line represents the cornea of eye 101. The retina is to theright.

In FIG. 4A the overall image size is small when fixation target 1082 isin focus on the retina. FIG. 5A illustrates the image 5082A on theretina of eye 101 produced by fixation target 1082 of fixation targetsystems 2000 and 3000 when fixation target 1082 is in a first locationwith respect to eye 101 near its far focal point, for example within 0.5diopters or less of its far focal point, preferably at a far distancewhere eye 101 has sufficient accommodation such that fixation target1082 remains in focus on the retina. Here it is assumed that fixationtarget 1082 comprises a series of concentric circles with fourcross-hairs spaced at 45 degree angle and which all cross at the centerof the circles.

When fixation target 1082 is fogged as shown in FIG. 4B, the image offixation target 1082 forms in front of the retina and the rays expand asthey continue on and the overall illuminated region on the retinaincreases. FIG. 5B illustrates the image 5082B on the retina of eye 101produced by fixation target 1082 of fixation target systems 2000 and3000 when target 1082 is moved further away from eye 101 so as toproduce fogging. It can be seen that image 5082B is actually larger thanimage 5082A due to the blurring. This creates the conflicting cuesbecause the blur cues tell the brain that fixation target 1082 has movedmore distant from eye 101, but the size of the image of fixation target1082 on the retina is a cue which tells the brain that fixation target1082 has moved closer to eye 101.

The in-focus image 5082A looks clear with uniform features. However,when second movable stage 1089 moves to fog target 1082 in fixationtarget system 3000, several defects appear in image 5082B.

First, the formerly thin lines of image 5082A become wider in image5082B. This is a near cue which indicates to a viewer that fixationtarget 1082 has actually moved nearer to eye 101.

Second, where lines intersect in image 5082A, enlarged ball linefeatures form in image 5082B. This is a near cue which indicates to aviewer that fixation target 1082 has actually moved nearer to eye 101.

Third, the very center of image 5082A, where many line intersect, alarge ball seems to form in image 5082B. This is a near cue whichindicates to a viewer that fixation target 1082 has actually movednearer to eye 101.

Fourth, lines in image 5082A extend outside the circular field of viewthat the optics of the optical system (e.g., lenses 1082, 1084 and 1085)allow of the fixation target (e.g., fixation target 1082). So for allfog positions, the overall extent of the fixation target remains thesame. This is a near cue which indicates to a viewer that fixationtarget 1082 has actually moved nearer to eye 101.

In practice, some observers say that when they look at a fixation target1082 in fixation target systems 3000 during the fogging stage motion,target 1082 seems to take on a three-dimensional appearance. This isalso an indication of a conflicting cue. When objects are far away, allthe features in them seem to shrink uniformly in size. But when objectsare close, people notice perspective cues. Parts of an object that arecloser appear larger while parts of the same object appear smaller. Whenparts within a single perceived objected take on different sizes, thatbrain interprets that as meaning the entire object is near. The growthof ball like features forming at intersecting lines is a near cue. Whenpeople see an object that is far away, features within the object areseen to remain constant size with respect to each other.

For many people, these conflicting cues prevent eye 101 from fullyrelaxing its accommodation. Because autorefractors and aberrometers arenot completely reliable in fully relaxing the accommodation of asignificant percentage of patients' eyes, the resulting refractionmeasurements are often erroneous or inaccurate.

Target 1082 is typically a back illuminated piece of film, and thus itis not possible to alter target 1082 as it is being projected to eye 101to compensate for distracting features that form in the image due topoor Bokeh control.

It would be desirable to apply principals of Bokeh optimization toprovide an optical stimulus in an optical measurement instrument such asa wavefront aberrometer or autorefractor that is more effective indrawing out the eye's refractive state than fixation targets which areemployed in existing optical measurement instruments.

One means of preventing bad Bokeh is to use images that are less proneto developing distracting feature than others such as a Siemens star:

.

However, that also prevents use of some image patterns that are likelyto be more effective in drawing the eye to its far point. Also onedesirable feature of a target is a horizontal line to help stabilizedthe eye, and the Siemens star lacks such a feature.

To address one or more of these issues, the inventors have conceived anddeveloped a fixation target system 6000 which is illustrated in FIG. 6which employs Bokeh compensation. Fixation target system 6000 is similarto fixation target system 3000, and a description of the same parts willnot be repeated. Different from fixation target system 3000, fixationtarget system 6000 includes a video display device 6082 which displays afixation target 7082 in the form of a video. Here, the video can changefixation target 7082 dynamically while fixation target 7082 is movedaway from eye 101 to measure one or more characteristics of eye 101, soas to provide Bokeh compensation for the image which is projected on theretina of eye 101.

For example, considering the fours defect identified above with respectto FIGS. 5A and 5B, in some embodiments correcting the defects can bedone by four primary means described below.

The first problem is a thin line that becomes appears wider when theBadal stage moves to fog the target. This can be corrected simply bydisplaying a fixation target which starts with wider lines, and then, asthe movable stage moves to fog the eye, the system can dynamicallychange the image which is being display to eye 101 to have thinnerlines, by means of a playing a video on video display device 6082 asfixation target 7082.

The second problem is that where lines intersect, balls seem to formduring fogging. This can be corrected by dynamically reducing thebrightness of the pixels that near the intersections. This may be doneby reducing pixel brightness, or tapering of the lines in an area wherethe lines interest, as the fixation target is moved away from eye 101and the video is played on video display device 6082.

The third problem is the large ball forming in the very center of thefixation target A solution for that is the same as the previous one:taper the pixel brightness down toward the center where theintersections are.

A fourth problem occurs when the lines of the fixation target overfillthe circular field of view of the optics of the optical system (e.g.,lenses 1082, 1084 and 1085). A solution to this problem is to use afixation target where the lines terminate within the field of view ofthe eye and do not extend beyond the field of view.

Beneficially, these adjustments may become stronger as the fog motionproceeds.

FIG. 7A illustrates an example of a fixation target 7082A which may beemployed in the fixation target system 6000 of FIG. 6.

Fixation target 7082A comprises a cross formed by two lines, including ahorizontal line 7002 and a vertical line 7004, intersecting at anintersection 7006.

FIGS. 7B and 7C illustrate examples of the fixation target 7082A of FIG.7A with Bokeh compensation applied.

In FIG. 7B, we see fixation target 7082B which is a result of employedBokeh compensation to fixation target 7082A. In particular, in FIG. 7Bprocessor 1040 is configured to control video display device 6082 todynamically reduce a thickness of the horizontal line and a thickness ofthe vertical line as video display device 6082 is moved further awayfrom eye 101. Also, processor 1040 is configured to control videodisplay device 6082 to dynamically decrease an intensity of the cross ata region about the intersection of the lines as video display device6082 is moved further away from eye 101.

In FIG. 7C, we see fixation target 7082C which is a result of employedBokeh compensation to fixation target 7082A. In particular, in FIG. 7Cprocessor 1040 is configured to control the video display device tocause each of the horizontal line and the vertical line to have adynamically increasing taper down to the intersection as the videodisplay device is moved further away from the eye.

FIG. 8A is a flowchart of one example embodiment of a method 8000 ofproducing a fixation target which includes Bokeh compensation.

An operation 8005 includes modeling effects of the optical system andaberrations of the eye to determine a series of model fogged images ofthe fixation target on a retina of the eye as a function of a distancefrom the video display device to the eye. Programs such as Zemax arecapable of that kind of simulation. Such programs can model the effectsof the optics in the autorefractor and aberrometer, and also theaberrations of the human eye, for example blur caused by diffraction afinite size of the pupil (e.g., a diameter of 4 mm).

An operation 8010 includes analyzing the model fogged images to identifyfeatures in the model fogged images which are inconsistent with how thefixation target would appear as the video display device is moved moredistant from the eye while the fixation target was viewed directly bythe eye.

An operation 8015 includes creating a movie for display on a videodisplay device by performing inverse operations on the fixation targetaccording to the identified features in the model fogged images tocompensate for the identified features as a function of the distancefrom the video display device to the eye. Such computational techniquesinclude Gaussian blur and deblurring. Alternatively, ray trace methodsmay be used. Tools and techniques for performing such inverse operationsare known to those skilled in the art.

FIG. 8B is a flowchart of an example embodiment of a method 8000B ofmeasuring one or more characteristics of eye 101 with a wavefrontaberrometer such as wavefront aberrometer 1000 and fixation targetsystem 6000.

An operation 8020 includes aligning a measurement instrument, includingthe wavefront aberrometer 1000, to eye 101 to be measured.

An operation 8025 includes activating a fixation target system, such asfixation target system 6000 for patient fixation on target 1082.

An operation 8030 includes the at least one processor 1040 moving firstmovable stage 1088 with respect to eye 101 to a first stage positionwhere fixation target 1082 draws a focus of eye 101 to near its farpoint (e.g., within one diopter of its far point).

An operation 8035 includes stopping movement of first movable stage 1088with respect to eye 101 at the first stage position.

An operation 8040 includes, while first movable stage 1088 is stopped,moving second movable stage 1089 with respect to first movable stage1088 and eye 101 to a second stage position where fixation target 1082is moved away from eye 101 by an additional amount (e.g., 1.5 diopters)such that blur cues of fixation target 1082 indicate to the subject thatfixation target 1082 is moving away from eye 101 at a same time that asize of an image of fixation target 1082 on the retina of eye 101decreases.

Operation 8040 includes dynamically changing fixation target 1082 onvideo display device to compensate for Bokeh of fixation target 1082 asthe video display device is moved away from eye 101 by the additionalamount. The Bokeh-compensated video file may be produced by a methodsuch as method 8000A discussed above.

An operation 8045 includes flashing a probe light beam, and causingwavefront sensor 1020 to measures refraction of eye 101.

The principles of wavefront aberrometer 1000 including a fixation targetsystem such as fixation target system 6000 having Bokeh compensation,and an associated method of operation, as described above, may beapplied to an optical measurement instrument which includes additionalfunctionality, such as the ability to measure corneal topography and/orto make optical coherence tomography (OCT) measurements of interiorstructures of the eye. Embodiments of such an optical measurementinstrument, and methods of operation thereof, will now be described.

As shown in FIGS. 9A-9C, an optical measurement system 1, according tomany embodiments, is operable to provide for a plurality of measurementsof the human eye, including wavefront aberrometry measurements, cornealtopography measurements, and optical coherence tomography measurementsto measure characteristics of the cornea, the lens capsule, the lens andthe retina. Optical measurement system 1 includes a main unit 2 whichcomprises a base 3 and includes many primary subsystems of manyembodiments of the system 1. For example, externally visible subsystemsinclude a touch-screen display control panel 7, a patient interfaceassembly 4 and a joystick 8.

Patient interface 4 may include one or more structures configured tohold a patient's head in a stable, immobile and comfortable positionduring the diagnostic measurements while also maintaining the eye of thepatient in a suitable alignment with the diagnostic system. In aparticularly preferred embodiment, the eye of the patient remains insubstantially the same position relative to the diagnostic system forall diagnostic and imaging measurements performed by the system 1.

In one embodiment the patient interface includes a chin support 6 and/ora forehead rest 4 configured to hold the head of the patient in asingle, uniform position suitably aligned with respect to the system 1throughout the diagnostic measurement. As shown in FIG. 9C, the opticalmeasurement system 1 may be disposed so that the patient may be seatedin a patient chair 9. Patient chair 9 can be configured to be adjustedand oriented in three axes (x, y, and z) so that the patent's head canbe at a suitable height and lateral position for placement on thepatient interface.

In many embodiments, the system 1 may include external communicationconnections. For example, the system 1 can include a network connection(e.g., an RJ45 network connection) for connecting the system 1 to anetwork. The network connection can be used to enable network printingof diagnostic reports, remote access to view patient diagnostic reports,and remote access to perform system diagnostics. The system 1 caninclude a video output port (e.g., HDMI) that can be used to outputvideo of diagnostic measurements performed by the system 1. The outputvideo can be displayed on an external monitor for, for example, viewingby physicians or users. The output video can also be recorded for, forexample, archival purposes. The system 1 can include one or more dataoutput ports (e.g., USB) to enable export of patient diagnostic reportsto, for example, a data storage device or a computer readable medium,for example a non-volatile computer readable medium, coupled to a lasercataract surgery device for use of the diagnostic measurements inconducting laser cataract surgeries. The diagnostic reports stored onthe data storage device or computer readable medium can then be accessedat a later time for any suitable purpose such as, for example, printingfrom an external computer in the case where the user without access tonetwork based printing or for use during cataract surgery, includinglaser cataract surgery.

FIG. 10 is a block diagram of a system including an optical measurementinstrument 1 according to one or more embodiments described herein.Optical measurement instrument 1 includes: an optical coherencetomographer (OCT) subsystem 10, a wavefront aberrometer subsystem 20,and a corneal topographer subsystem 30 for measuring one or morecharacteristics of a subject's eye. Optical measurement instrument 1 mayfurther include an iris imaging subsystem 40, a fixation targetsubsystem 50, a controller 60, including one or more processor(s) 61 andmemory 62, a display 70 and an operator interface 80. Opticalmeasurement instrument 1 further includes a patient interface 4 for asubject to present his or her eye for measurement by optical measurementinstrument 1.

The optical coherence tomography subsystem 10 is configured to measurethe spatial disposition (e.g., three-dimensional coordinates such as X,Y, and Z of points on boundaries) of eye structures in three dimensions.Such structure of interest can include, for example, the anteriorsurface of the cornea, the posterior surface of the cornea, the anteriorportion of the lens capsule, the posterior portion of the lens capsule,the anterior surface of the crystalline lens, the posterior surface ofthe crystalline lens, the iris, the pupil, the limbus and/or the retina.The spatial disposition of the structures of interest and/or of suitablematching geometric modeling such as surfaces and curves can be generatedand/or used by the controller for a number of purposes, including, insome embodiment to program and control a subsequent laser-assistedsurgical procedure. The spatial disposition of the structures ofinterest and/or of suitable matching geometric modeling can also be usedto determine a wide variety of parameters.

As a non-limiting example, the system 1 can be configured to use a sweptsource OCT imaging system employing wavelengths of around 1060 nm withan 8 mm scan depth. The spatial disposition of the eye structures usingoptical coherence tomography should generally be measured while thepatient is engaged with patient interface 4. The OCT scan depth may bebetween 8 and 50 mm, and the scan depth may be greater than about 24 mmor even 30 mm to achieve a full eyescan depth. The swept sourcewavelengths can be centered at wavelengths from 840 nm to 1310 nm.

Optical coherence tomographer subsystem 10 is only one example of an eyestructure imaging subsystem which may be employed in optical measurementinstrument 1. In other embodiments, a different eye structure imagingsubsystem may be employed, for example a Scheimplug Imager, afluorescence imager, a structured lighting imager, a wavefronttomographer, an ultrasound imager and a plenoptic imager.

The wavefront aberrometer subsystem 20 is configured to measure ocularaberrations, which may include low and high order aberrations, bymeasuring the wavefront emerging from the eye by, for example a ShackHartman sensor.

The corneal topographer subsystem 30 may apply any number of modalitiesto measure the shape of the cornea including one or more of akeratometry reading of the eye, a corneal topography of the eye, anoptical coherence tomography of the eye, a Placido disc topography ofthe eye, a reflection of a plurality of points from the corneatopography of the eye, a grid reflected from the cornea of the eyetopography, a Hartmann-Shack measurement of the eye, a Scheimpflug imagetopography of the eye, a confocal tomography of the eye, a Helmholtzsource topographer, or a low coherence reflectometry of the eye. Theshape of the cornea should generally be measured while the patient isengaged with patient interface 4.

Fixation target system 50 is configured to control the patient'saccommodation, as described above. In some embodiments, fixation targetsystem 50 may be implemented by fixation target system 1080 and fixationtarget system 6000 which presents a Bokeh-compensated fixation target ona video display device.

Images captured by the corneal topographer subsystem 10, the wavefrontaberrometer 20, the optical coherence tomographer subsystem 30 or thecamera 40 may be displayed with a display of the operator interface 80of the optical measurement system 2 or the display 70 of the opticalmeasurement system, respectively. The operator interface may also beused to modify, distort, or transform any of the displayed images.

The shared optics 55 provide a common propagation path that is disposedbetween the patient interface 4 and each of the optical coherencetomographer (OCT) subsystem 10, the wavefront aberrometer subsystem 20,the corneal topographer subsystem 30, and in some embodiments, thecamera 40, and the fixation target system 50. In many embodiments, theshared optics 55 may comprise a number of optical elements, includingmirrors, lenses and beam combiners to receive the emission from therespective subsystem to the patient's eye and, in some cases, toredirect the emission from a patient's eye along the common propagationpath to an appropriate director.

The controller 60 controls the operation of the optical measurementinstrument 1 and can receive input from any of the optical coherencetomographer (OCT) subsystem 10, the wavefront aberrometer subsystem 20,the corneal topographer subsystem 30 for measuring one or morecharacteristics of a subject's eye, the camera 40, the fixation targetsystem 50, the display 70 and the operator interface 80 via thecommunication paths 58. The controller 60 can include any suitablecomponents, such as one or more processor, one or morefield-programmable gate array (FPGA), and one or more memory storagedevices. In many embodiments, the controller 60 controls the display 70to provide for user control over the laser eye surgery procedure forpre-cataract procedure planning according to user specified treatmentparameters as well as to provide user control over the laser eye surgeryprocedure. The communication paths 58 can be implemented in any suitableconfiguration, including any suitable shared or dedicated communicationpaths between the controller 60 and the respective system components.

The operator interface 80 can include any suitable user input devicesuitable to provide user input to the controller 60. For example, theuser interface devices 80 can include devices such as joystick 8, akeyboard or a touchscreen display 70.

FIGS. 11A and 11B are simplified block diagrams illustrating an assembly100 according to many embodiments which may be included in system 1. Theassembly 100 is a non-limiting example of suitable configurations andintegration of the optical coherence tomographer (OCT) subsystem 190,the wavefront aberrometer subsystem 150, the corneal topographersubsystem 140 for measuring one or more characteristics of a subject'seye, a camera 40, the fixation target subsystem 180 and the sharedoptics.

The shared optics generally comprise one or more components of a firstoptical system 170 disposed along a central axis 102 passing through theopening or aperture 114 of the structure 110. A first optical system 170directs light from the various light sources along the central axis 102towards the eye and establishes a shared or common optical path alongwhich the light from the various light sources travel to the eye 101. Inone embodiment, optical system 170 comprises a quarter wave plate 171, afirst beamsplitter 172, a second beamsplitter 173, an optical element(e.g., a lens) 174, a second lens 175, a third beamsplitter 176, and astructure including an aperture 178. Additional optical systems may beused in assembly 100 to direct light beams from one or more lightsources to the first optical system 170. For example, a second opticalsystem 160 directs light to the first optical system 170 from thewavefront aberrometer subsystem 150 and comprises mirror 153, beamsplitter 183 and lens 185.

Other configurations of the assembly 100 may be possible and may beapparent to a person of skill in the art.

The corneal topographer subsystem 140 comprises a structure 110 having aprincipal surface 112 with an opening or aperture 114 therein; aplurality of first (or peripheral) light sources 120 provided on theprincipal surface 112 of the structure 110; a Helmholz light source 130;and a detector, photodetector, or detector array 141.

In one embodiment, structure 110 has the shape of an elongated oval or“zeppelin” with openings or apertures at either end thereof. An exampleof such a structure is disclosed in Yob ani Meji′a-Barbosa et al.,“Object surface for applying a modified Hartmann test to measure cornealtopography,” APPLIED OPTICS, Vol. 40, No. 31 (Nov. 1, 2001)(“Meji′a-Barbosa”). In some embodiments, principal surface 112 ofstructure 110 is concave when viewed from the cornea of eye 100, asillustrated in FIG. 11A.

In one embodiment where principal surface 112 is concave, principalsurface 112 has the shape of a conical frustum. Alternatively, principalsurface 112 may have a shape of hemisphere or some other portion of asphere, with an opening or aperture therein. Also alternatively,principal surface 112 may have the shape of a modified sphere or conicalfrustum, with a side portion removed. Beneficially, such an arrangementmay improve the ergonomics of assembly 100 by more easily allowingstructure 110 to be more closely located to a subject's eye 100 withoutbeing obstructed by the subject's nose. Of course, a variety of otherconfigurations and shapes for principal surface 112 are possible.

In the embodiment of FIG. 11A, the plurality of first light sources 120are provided on the principal surface 112 of structure 110 so as toilluminate the cornea of eye 101. In one embodiment, light sources 122may comprise individual light generating elements or lamps, such aslight emitting diodes (LEDs) and/or the tips of the individual opticalfibers of a fiber bundle. Alternatively, principal surface 112 ofstructure 110 may have a plurality of holes or apertures therein, andone or more backlight lamps, which may include reflectors and/ordiffusers, may be provided for passing lighting through the holes toform the plurality of first light sources 120 which project light ontothe cornea of eye 100. Other arrangements are possible.

In another embodiment, structure 110 is omitted from assembly 100, andthe first light sources 120 may be independently suspended (e.g., asseparate optical fibers) to form a group of first light sources 120arranged around a central axis, the group being separated from the axisby a radial distance defining an aperture in the group (correspondinggenerally to the aperture 114 in the structure 110 illustrated in FIG.11A).

In operation, a ray (solid line) from one of the first light sources 120is reflected by the cornea and passes through optical system 170(including aperture 178) to appear as a light spot on detector array141. It will be appreciated that this ray is representative of a smallbundle of rays that make it through optical system 170 and onto detectorarray 141, all of which will focus to substantially the same location ondetector array 141. Other rays from that first light source 120 areeither blocked by the aperture 178 or are otherwise scattered so as tonot pass through the optical system 170. In similar fashion, light fromthe other first light sources 120 are imaged onto detector array 141such that each one of first light sources 120 is imaged or mapped to alocation on detector array 141 that may be correlated to a particularreflection location on the cornea of eye 100 and/or the shape of thecornea. Thus, detector array 141 detects the light spots projectedthereon and provides corresponding output signals to a processor ofcontroller 60 (FIG. 10). The processor determines the locations and/orshape of the light spots on detector array 141, and compares theselocations and/or shapes to those expected for a standard or modelcornea, thereby allowing the processor of controller 60 to determine thecorneal topography. Alternatively, other ways of processing the spotimages on detector array 141 may be used to determine the cornealtopography of eye 101, or other information related to thecharacterization of eye 101.

Detector array 141 comprises a plurality of light detecting elementsarranged in a two dimensional array. In one embodiment, detector array141 comprises such a charge-coupled device (CCD), such as may be foundin a video camera. However, other arrangements such as a CMOS array, oranother electronic photosensitive device, may be employed instead.Beneficially, the video output signal(s) of detector array 141 areprovided to processor 61 which processes these output signals asdescribed in greater detail below.

Assembly 100 also comprises a Helmholtz light source 130 configuredaccording to the Helmholtz principle. As used herein, the term“Helmholtz source” or “Helmholtz light source” means one or a pluralityof individual light sources disposed such that light from each of theindividual light sources passes through an optical element havingoptical power, reflects off of a reference or test object, passesthrough the optical element, and is received by a detector, whereinlight from the Helmholtz source is used to determine geometric and/oroptical information of at least a portion of a surface of the referenceor test object. In general, it is a characteristic of Helmholtz sourcesthat the signal at the detector is independent of the relative positionof the test or reference object relative to the Helmholtz source. Asused herein, the term “optical element” means an element that refracts,reflects, and/or diffracts light and has either positive or negativeoptical power.

In such embodiments, the Helmholtz light source 130 is located atoptical infinity with respect to eye 100. The Helmholtz principleincludes the use of such infinite sources in combination with atelecentric detector system: i.e., a system that places the detectorarray at optical infinity with respect to the surface under measurement,in addition to insuring that the principal measured ray leaving thesurface is parallel to the optical axis of the instrument The Helmholtzcorneal measurement principle has the Helmholtz light source at opticalinfinity and the telecentric observing system so that detector array 141is also optically at an infinite distance from the images of the sourcesformed by the cornea. Such a measurement system is insensitive to axialmisalignment of the corneal surface with respect to the instrument.

In one embodiment, the Helmholtz light source 130 comprises a secondlight source 132 which may comprise a plurality of lamps, such as LEDsor optical fiber tips. In one embodiment, second light source 132comprises an LED and a plate 133 with plurality of holes or apertures ina surface that are illuminated by one or more backlight lamps with anoptical element 131, which may comprise diffusers.

In one embodiment, second light sources 132 are located off the centraloptical axis 102 of assembly 100, and light from second light sources132 is directed toward optical element 171 by third beam splitter 176.

The operation of the topographer portion of system 100 may be conductedwith the combined use of first light source 120 and the Helmholz lightsource 130. In operation, detector array 141 detects the light spotsprojected thereon from both Helmholz light source 130 (detected at acentral portion of detector array 141) and first light sources 120(detected at a peripheral portion of detector array 141) and providescorresponding output signals to processor. In general, the images offirst light sources 120 that appear on detector array 140 emanate froman outer region of the surface of the cornea, and the images of Helmholzlight source 130 that appear on detector array 141 emanate from acentral or paraxial region of the surface of the cornea. Accordingly,even though information about the central region of the corneal surface(e.g., surface curvature) cannot be determined from the images of firstlight sources 120 on detector array 141, such information can bedetermined from the images of Helmholz light source 130 on detectorarray 141. A processor of controller 60 determines the locations and/orshapes of the light spots on detector array 141, and compares theselocations and/or shapes to those expected based for a standard or modelcornea, thereby allowing the processor to determine the cornealtopography of eye 101. Accordingly, the topography of the entire cornealsurface can be characterized by system 100 without a “hole” or missingdata from the central corneal region.

A fourth light source 201 off the central axis 102 may be directed alongoptical axis 102 by mirrors 177, 179 disposed on or near the aperture178, perpendicular to the optical axis 102 are configured as a pupilretroreflection illuminator. The pupil retroreflecton illuminator isconfigured to direct a disc of light toward a patient's eye, whereby thedisc of light may be reflected from reflective surfaces within the eye,and the reflected light is transmitted by optical path 170 to detector141. The pupil retroreflection illuminators may optionally be configuredsuch that, when a patient's pupil is dilated, the disc of light fromlight source 201 is reflected from an implanted IOL to image the IOL,including any fiducial marks; if IOL is imperfectly placed, detector 141may be used to determine IOL edges are decentered. Also, images fromdetector 141 using the pupil retroreflection illuminator may see folds,for instance, unfolded edge if the IOL did not unfold properly.

The wavefront aberrometer subsystem 150 of the assembly 100 comprises athird (probe light beam) light source 152 providing a probe light beamand a wavefront sensor 155. Wavefront aberrometer subsystem 150 mayfurther comprise: a collimating lens 154; a polarizing beamsplitter 163;and an imaging system 166 comprising a first optical element, lens 163and a second optical element, lens 164, and a dynamic-range limitingaperture 165 for limiting a dynamic range of light provided to wavefrontsensor 155 so as to preclude data ambiguity. Light from the wavefrontaberrometer subsystem is directed to one of the constituent opticalelements of the optical system 170 disposed along a central axis 102passing through the opening or aperture 114 of the structure 110. Itwill be appreciated by those of skill in the art that the lenses 163,164, or any of the other lenses discussed herein, may be replaced orsupplemented by another type of converging or diverging optical element,such as a diffractive optical element.

Light source 152 may be an 840 nm SLD (super luminescent laser diode).An SLD is similar to a laser in that the light originates from a verysmall emitter area. However, unlike a laser, the spectral width of theSLD is very broad, about 40 nm. This tends to reduce speckle effects andimprove the images that are used for wavefront measurements.

Wavefront sensor 155 may be a Shack-Hartmann wavefront sensor comprisinga detector array and a plurality of lenslets for focusing received lightonto its detector array. In that case, the detector array may be a CCD,a CMOS array, or another electronic photosensitive device. However,other wavefront sensors may be employed instead. Embodiments ofwavefront sensors which may be employed in one or more systems describedherein are described in U.S. Pat. No. 6,550,917, issued to Neal et al.on Apr. 22, 2003, and U.S. Pat. No. 5,777,719, issued to Williams et al.on Jul. 7, 1998, both of which patents are hereby incorporated herein byreference in their entirety.

The aperture or opening in the middle of the group of first lightsources 120 (e.g., aperture 114 in principal surface 112 of structure110) allows system 100 to provide a probe light beam into eye 101 tocharacterize its total ocular aberrations. Accordingly, third lightsource 152 supplies a probe light beam through polarizing beam splitter162 to first beamsplitter 172 of optical system 170. First beamsplitter172 directs the probe light beam through aperture 114 to eye 101.Beneficially, light from the probe light beam is scattered from theretina of eye 100, and at least a portion of the scattered light passesback through aperture 114 to first beamsplitter 172. First beamsplitter172 directs the back scattered light back through beam splitter 172 topolarizing beamsplitter 183, mirror 153, adjustable focal length lens179, and ultimately to wavefront sensor 155.

Wavefront sensor 155 outputs signals to a processor ofcontroller/processor 60 which uses the signals to determine ocularaberrations of eye 101, including measuring the refraction of eye 101.Beneficially, controller/processor 60 may be able to better characterizeeye 101 by considering the corneal topography of eye 101 measured by thecorneal topography subsystem, which may also be determined bycontroller/processor 60 based on outputs of detector array 141, asexplained above.

In operation of the wavefront aberrometer subsystem 150, light fromlight source 152 is collimated by lens 154. The light passes throughlight source polarizing beam splitter 162. The light entering lightsource polarizing beam splitter 162 is partially polarized. Polarizingbeam splitter 162 reflects light having a first, S, polarization, andtransmits light having a second, P, polarization so the exiting light is100% linearly polarized. In this case, S and P refer to polarizationdirections relative to the hypotenuse in light source polarizing beamsplitter 162.

The light from polarizing beamsplitter 162 travels through adjustablefocal length lens 179 and passes through toward beam splitter 153,retaining its S polarization, and then travels through beamsplitter 183,optical element (e.g., lens) 185, beamsplitter 172 and 173, and quarterwave plate 171. Quarter wave plate 171 converts the light to circularpolarization. The light then travels through aperture 114 in principalsurface 112 of structure 110 to eye 101. Beneficially, the beam diameteron the cornea may be between 1 and 2 mm. Then the light travels throughthe cornea and focuses onto the retina of eye 101.

The focused spot of light becomes a light source that is used tocharacterize eye 101 with wavefront sensor 155. Light from the probelight beam that impinges on the retina of eye 101 scatters in variousdirections. Some of the light reflects back as a semi-collimated beamback towards assembly 100. Upon scattering, about 90% of the lightretains its polarization. So the light traveling back towards assemblyis substantially still circularly polarized. The light then travelsthrough aperture 114 in principal surface 112 of structure 110, throughquarterwave plate 171, and is converted back to linear polarization.Quarterwave plate 171 converts the polarization of the light from theeye's retina so that it is P polarized, in contrast to probe light beamhaving the S polarization. This P polarized light then reflects off offirst beamsplitter 172, and passes through optical element (e.g., lens)185, beamsplitters 183 and 153, optical element (e.g., lens) 168 andreaches polarizing beamsplitter 162. Since the light is now P polarizedrelative the hypotenuse of polarizing beamsplitter 162, the beam istransmitted and then continues to imaging system 166 comprising firstoptical element 164 and second optical element (e.g., lens) 163. Thebeam is also directed through a dynamic-range limiting aperture 165 forlimiting a dynamic range of light provided to wavefront sensor 155 so asto preclude data ambiguity.

When wavefront sensor 155 is a Shack-Hartmann sensor, the light iscollected by the lenslet array in wavefront sensor 155 and an image ofspots appears on the detector array (e.g., CCD) in wavefront sensor 155.This image is then provided to be processed by controller/processor 60and analyzed to compute the refraction and aberrations of eye 101.

The comprises a pre-correction system which compensates the probe lightbeam 153 to be injected into eye 101 for aberrations in eye 101 byadding a desired pre-correction for the injected probe light beam 153 byadding defocus that just compensates for the spherical equivalentdefocus of eye 101 which is being measured. Movable stage 1130 may bemoved in response to control signal 199 which may be provided fromcontroller/processor 60.

The same position of movable stage 1130 which corrects for the defocusaberrations of eye 101, also ensures that the returned light arrives ata wavefront sensor 155 collimated to within the dynamic range ofwavefront sensor 155. Dynamic range limiting aperture 165 blocks anyrays outside the angular dynamic range of the wavefront sensor 155 sothat no mixing or measurement confusion occurs. When the wavefrontsensor 155 is a Shack-Hartmann sensor, the focal spots cannot collide,interfere or cause confusion with adjacent focal spots.

Beneficially, controller/processor 60 moves movable stage 1130 toprovide a desired characteristic to at least one of: probe light beam153 injected into eye 101, or the light received by wavefront sensor 155from the retina of eye 101.

The proper or desired adjusted focal length for movable stage 1130 maybe determined in a number of ways. In some embodiments, an additionalbeam splitter may be provided in an optical path between imaging system166 and wavefront sensor 155, and a focusing lens and a detector may beused to create an image of the light incident upon the retina. In thatcase, the proper or desired adjusted focal length may be determined byminimizing the spot size on the back of the retina, performed bycomparing the spot sizes from different focal length values foradjustable focal length lens 169. Beneficially eye 101 is arranged to beone focal length of objective lens 168, and wavefront sensor 155 isarranged to be at the conjugate image plane to eye 101.

Meanwhile, controller/processor 60 receives image data (“first imagedata”) from wavefront sensor 155 produced in response to the lightreturned from the retina of eye 101, and processes the first image datato determine the refraction of eye 101.

An OCT subsystem 190 of assembly 100 may comprise an OCT assembly 191,and a third optical path 192 which directs the OCT beam of the OCT lightsource to the first optical path 170. The third optical path 192 maycomprise a fiber optic line 196, for conducting the OCT beam from theOCT light source, a z-scan device 193 operable to alter the focus of thebeam in the z-direction (i.e., along the direction of propagation of theOCT beam) under control of the controller, and x-scan device 195, and ay-scan device 197 operable to translate the OCT beam in the x and ydirections (i.e., perpendicular to the direction of propagation of theof the OCT beam), respectively, under control of the controller. The OCTlight source and reference arm may be incorporated into the main unit 4of the optical measurement instrument 1 shown in FIG. 9A. Alternatively,the OCT assembly 191 may be housed in a second unit 200 and the OCT beamfrom the OCT source may be directed from the second housing 200 to themain unit by optical pathway 192.

The OCT systems and methods of the optical measurement instruments andmethods described herein may be FD-OCT (Fourier domain optical coherencetomography) systems, including either an SD-OCT (spectral domain opticalcoherence tomography) system or an SS-OCT (swept source opticalcoherence tomography) system. In conventional FD-OCT systems, theinterference signal is distributed and integrated over numerous spectralwavelength intervals, and is inverse Fourier transformed to obtain thedepth-dependent reflectivity profile of the sample. The profile ofscattering as a function of depth is referred to as an A-scan(Axial-scan). The beam can be scanned laterally to produce a set ofA-scans that can be combined together to form a tomogram of the sample(a B-scan).

In an SD-OCT system, various spectral wavelength intervals of thecombined returned light from the reference and sample arms are spatiallyencoded using, for instance, a collimator, diffraction grating, and alinear detector array. Resampling of the data obtained from the lineardetector array is performed in order to correct for the nonlinearspatial mapping of wavenumbers. After resampling and subtraction of thedc background, the depth profile structural information is obtained byperforming the inverse Fourier transform operation. In swept-source OCT,the broad bandwidth optical source is replaced by a rapid-scanning lasersource. By rapidly sweeping the source wavelength over a broadwavelength range, and collecting all the scattering information at eachwavelength and at each position, the composition of the collected signalis equivalent to the spectral-domain OCT technique. The collectedspectral data is then inverse Fourier transformed to recover the spatialdepth-dependent information.

FD-OCT suffers from an inherent sample-independent limited depth range,typically between 1 and 5 mm. One limitation flows from the fact thatFD-OCT extracts depth information from the inverse Fourier transform ofa spectral interferogram. Since the spectral interferogram can only berecorded as a real signal, its Fourier transform is necessarilyHermitian symmetric about the zero path length difference (ZPD)position. As a result, the positive and negative displacements about theZPD cannot be unambiguously resolved, which gives rise to mirror imageartifacts and generally halves the useable range. This is referred to asthe complex conjugate ambiguity. Another limitation is a sensitivityfall-off which results in reduced sensitivity with increasing depth.Moreover, since the signal in OCT is derived only from backscatteredphotons, optical attenuation from absorption and scattering generallyresult in a useable imaging depth of about 1-4 mm.

Several “full range” OCT techniques have been developed that eliminatethe complex conjugate artifacts to effectively double the measurementrange around the ZPD position. These full range OCT techniques result inuseable imaging depths of up to about 5 mm up to about 8 mm. Suitablefull range techniques are methods utilizing a dithering reference lag tobreak the phase ambiguity, methods that use phase distortion, and othersuitable methods

As shown in FIG. 12, the OCT assembly 191 of OCT subsystem 190 includesa broadband or a swept light source 202 that is split by a coupler 204into a reference arm 206 and a sample arm 210. The reference arm 106includes a module 108 containing a reference reflection along withsuitable dispersion and path length compensation. The sample arm 110 ofthe OCT assembly 191 has an output connector 212 that serves as aninterface to the rest of the optical measurement instrument. The returnsignals from both the reference and sample arms 206, 210 are thendirected by coupler 204 to a detection device 220, which employs eithertime-domain, frequency, or single point detection techniques. In FIG.12, a swept source technique is used with a laser wavelength of 1060 nmswept over a range of 8-50 mm depth.

FIG. 13 is a schematic drawing of a human eye 400. In many embodiments,a light beam 401 from a light source enters the eye from the left ofFIG. 13, refracts into the cornea 410, passes through the anteriorchamber 404, the iris 406 through the pupil, and reaches lens 402. Afterrefracting into the lens, light passes through the vitreous chamber 412,and strikes the retina 476, which detects the light and converts it toan electric signal transmitted through the optic nerve to the brain (notshown). The vitreous chamber 412 contains the vitreous humor, a clearliquid disposed between the lens 402 and retina 476. As indicated inFIG. 13, cornea 410 has corneal thickness (CT), here considered as thedistance between the anterior and posterior surfaces of the cornea.Anterior chamber 404 has anterior chamber depth (ACD), which is thedistance between the anterior surface of the cornea and the anteriorsurface of the lens. Lens 402 has lens thickness (LT) which is thedistance between the anterior and posterior surfaces of the lens. Theeye has an axial length (AXL) which is the distance between the anteriorsurface of the cornea and the retina 476. FIG. 13 also illustrates that,in many subjects the lens, including the lens capsule, may be tilted atone or more angles relative to the optical axis, including an angle γrelative to the optical axis of the eye.

The optical system may also be arranged so that the movement pattern ofthe scan mirrors provides a lateral motion across the retina so that theshape of the retina may be determined. It is of particular interested tomeasure the shape and location of the depressed region of the retinanamed the foveal pit. When the patient is looking directly into theinstrument, with their line of sight aligned to the fixation target, thefoveal pit will be in center of the OCT lateral scan. This informationis beneficial in that it informs the instrument operator if the patientwas looking directly at the target when the measurement was made.Retinal scans are also useful in detecting disease conditions. In somecases there may be an absence of a foveal pit that also is considered anindication of a corneal abnormality.

The average axial length of the adult human eye is about 24 mm. Sincethe full range imaging depth of the OCT measurements are only about 5 mmto 8 mm, then OCT scanning may provide for OCT scans at different depthsof the eye that can be combined together to form a combined OCT image ofthe eye. The OCT measurements may include OCT imaging at various depthsof the patient's eye for imaging: (1) at least a portion of the retina,(2) at least a portion of the anterior portion of the eye, including atleast a portion of the cornea (anterior and posterior), iris, and lens(anterior and posterior), and (3) performing axial eye lengthmeasurements.

FIGS. 14A-14C illustrate various aspects of the OCT subsystem 190according to various aspects of the present invention. FIG. 14Aillustrates a preferred scanning region for the OCT subsystem accordingto many embodiments of the present invention. The scanning region may bedefined from starting point 301 to ending point 302 at the anteriorportion of the eye extending in a direction transverse the direction ofpropagation of the OCT beam and also extending in a direction parallelto an axis defining the axial length of the eye to the posterior portion304 of the eye. The lateral scanning region should generally besufficiently large in the lateral direction to permit imaging of thecentral portion of the cornea, at least a portion of the iris, at leasta portion of the lens and at least of the retina. It should be notedthat a region 303 between the posterior portion of the lens and thesurface of the retina may optionally not be scanned by OCT subsystem 190because the portion 330 does not contain anatomical structure for 3Danalysis.

FIG. 14B shows a representative graph of an intensity of an OCT signalof an OCT subsystem 190 according to many embodiments as a function ofdepth along the axis defining the axial length of the eye. The graphgenerally exhibits approximately four peaks having a complex structure:(1) a peak 310 having a doublet-like structure and generallycorresponding to a location of the cornea; (2) a peak 320 having adoublet-like structure and generally corresponding to a location of ananterior surface of the lens; (3) a peak 330 having a complex structuregenerally corresponding to a location of a posterior surface of thelens; and (4) a peak 340 generally corresponding to a location of aretina. A distance between peak 310 and peak 340 can be used tocalculate the axial length (AL) of the eye. An OCT scan by OCT subsystem190, including both an A-scan and B-scan, may be conducted for at leastone location in the anterior portion of the eye (e.g., a location of acornea, a location of an anterior surface of a lens and/or a location ofa posterior surface of the lens) and at least one location in theposterior portion of the eye (e.g., at a location of a retina). In someembodiments, an OCT scan by the OCT subsystem 190, including both anA-Scan and a B-scan is performed at a location corresponding to each ofa location of the cornea, a location of an anterior surface of the lens,a location of a posterior surface of the lens, and a locationcorresponding to a retina.

It should be noted that because the OCT subsystem 190 provides for thedetection of various structures of the eye, including a location of thecornea, the OCT subsystem 190 may be used as a ranging system toprecisely align the patient in relation to the optical measurementsystem 1 of the present invention. The use of the OCT as a rangingsystem can significantly improve accuracy of corneal topographymeasurements, including keratometry measurements, which are sensitive tomisalignment of the corneal structures.

FIG. 14C shows a cross-section of an eye obtained by an opticalmeasurement system of the present invention using an OCT subsystemaccording to the present invention.

FIG. 15 shows a 3 dimensional view of an eye obtained by an opticalmeasurement system of the present invention using an OCT subsystemaccording to the present invention. FIG. 15 evidences that the OCTsubsystem of the present invention is operable to obtain biometrymeasurements according to the present invention, including the centralcorneal thickness (CCT), the anterior chamber depth (ACD), the radius ofcurvature of the anterior cornea (ROC_(AC)), the radius of curvature ofthe Posterior cornea (ROC_(PC)) and the Radius of curvature of the axiallength (ROC_(AL)).

OCT subsystem 190 may provide sufficiently resolved structuralinformation to a structural assessment that may provide a user with anindication of suitability of a particular patient for a laser cataractprocedure. In one embodiment, an OCT scan performed by the OCT subsystem190 at or near the retina (i.e., a retina scan) is sufficiently resolvedto identify the foveal pit location and depth, wherein a lack ofdepression indicates an unhealthy retina.

In another embodiment, the optical measurement instrument 1 of thepresent invention provides one or more measurements sufficient toprovide an assessment of the tear film of a patient. In one embodiment,the tear film assessment comprises a comparison of a wavefrontaberrometry map and a corneal topography map or OCT map of the patient'seye, by, for instance, subtracting the corneal topography map from thewavefront aberrometry map, to obtain a difference map. A determinationof whether the tear film is broken (if not smooth); an assessment of thetear film, including tear film breakup, can be obtained by reviewing theshape of spots on the topographer. For instance, a finding or indicationthat the tear film is disrupted, or broken, may be based upon the shapeof a spot in that, if the spots are not round, and have, for instance,an oblong or broken up shape, it indicates that tear film is disrupted.The existence of such a disrupted tear film may indicate that K value,and other ocular measurements may not be reliable

In operation, as shown in FIG. 11A, after exiting connector 212, the OCTbeam 214 may be collimated, for example using a collimating opticalfiber 196. Following collimating fiber 196 the OCT beam 214 is directedto an z-scan device 193 operable to change the focal point of the OCTbeam in a z-direction, and x- and y-scan devices 195 and 197, which areoperable to scan the OCT beam in x and y-directions perpendicular to thez-direction.

Following the collimating optical fiber 196, the OCT beam 214 continuesthrough a z-scan device 193, 194. The z-scan device may be a Z telescope193, which is operable to scan focus position of the laser pulse beam 66in the patient's eye 101 along the Z axis. For example, the Z-telescopemay include a Galilean telescope with two lens groups (each lens groupincludes one or more lenses). One of the lens groups moves along the Zaxis about the collimation position of the Z-telescope 193. In this way,the focus position in the patient's eye 101 moves along the Z axis. Ingeneral, there is a relationship between the motion of lens group andthe motion of the focus point. The exact relationship between the motionof the lens and the motion of the focus in the z axis of the eyecoordinate system does not have to be a fixed linear relationship. Themotion can be nonlinear and directed via a model or a calibration frommeasurement or a combination of both. Alternatively, the other lensgroup can be moved along the Z axis to adjust the position of the focuspoint along the Z axis. The Z-telescope 84 functions as a z-scan devicefor changing the focus point of the OCT beam 214 in the patient's eye101. The Z-scan device can be controlled automatically and dynamicallyby the controller 60 and selected to be independent or to interplay withthe X and Y scan devices described next.

After passing through the z-scan device, the OCT beam 214 is incidentupon an X-scan device 195, which is operable to scan the OCT beam 214 inthe X direction, which is dominantly transverse to the Z axis andtransverse to the direction of propagation of the OCT beam 214. TheX-scan device 195 is controlled by the controller 60, and can includesuitable components, such as a lens coupled to a MEMS device, a motor,galvanometer, or any other well-known optic moving device. Therelationship of the motion of the beam as a function of the motion ofthe X actuator does not have to be fixed or linear. Modeling orcalibrated measurement of the relationship or a combination of both canbe determined and used to direct the location of the beam.

After being directed by the X-scan device 196, the OCT beam 214 isincident upon a Y scan device 197, which is operable to scan the OCTbeam 214 in the Y direction, which is dominantly transverse to the X andZ axes. The Y-scan device 197 is controlled by the controller 60, andcan include suitable components, such as a lens coupled to a MEMSdevice, motor, galvanometer, or any other well-known optic movingdevice. The relationship of the motion of the beam as a function of themotion of the Y actuator does not have to be fixed or linear. Modelingor calibrated measurement of the relationship or a combination of bothcan be determined and used to direct the location of the beam.Alternatively, the functionality of the X-Scan device 195 and the Y-Scandevice 197 can be provided by an XY-scan device configured to scan thelaser pulse beam 66 in two dimensions transverse to the Z axis and thepropagation direction of the laser pulse beam 66. The X-scan and Y scandevices 195, 197 change the resulting direction of the OCT beam 214,causing lateral displacements of OCT beam 214 located in the patient'seye 101.

The OCT sample beam 214 is then directed to beam splitter 173 throughlens 175 through quarter wave plate 171 and aperture 114 and to thepatient eye 101. Reflections and scatter off of structures within theeye provide return beams that retrace back through the patient interfacequarter wave plate 171, lens 175, beam splitter 173, y-scan device 197,x-scan device 195, z-scan device 193, optical fiber 196 and beamcombiner 204 (FIG. 12), and back into the OCT detection device 220. Thereturning back reflections of the sample arm 201 are combined with thereturning reference portion 206 and directed into the detector portionof the OCT detection device 220, which generates OCT signals in responseto the combined returning beams. The generated OCT signals that are inturn interpreted by the controller 60 to determine the spatialdisposition of the structures of interest in the patient's eye 101. Thegenerated OCT signals can also be interpreted by the controller todetermine the spatial disposition of the structures of interest in thepatient's eye 101. The generated OCT signals can also be interpreted bythe control electronics to align the position and orientation of thepatient eye within the patient interface.

Optical measurement systems disclosed herein may comprise an irisimaging subsystem 40. The imaging subsystem 40 generally may comprise aninfrared light source, for example an infrared light source 152, anddetector 141. In operation light from the light source 152 is directedalong second optical path 160 to first optical path 170 and issubsequently directed to eye 101 as described above. Light reflectedfrom the iris of eye 101 is reflected back along first optical path 170to detector 141. In normal use, an operator will adjust a position oralignment of system 100 in XY and Z directions to align the patientaccording to the image detector array 141. In one embodiment of the irisimaging subsystem, eye 101 is illuminated with infrared light from lightsource 152. In this way, the wavefront obtained by wavefront sensor 155will be registered to the image from detector array 141.

The image that the operator sees is the iris of eye 100. The corneagenerally magnifies and slightly displaces the image from the physicallocation of the iris. So the alignment that is done is actually to theentrance pupil of the eye. This is generally the desired condition forwavefront sensing and iris registration.

Iris images obtained by the iris imaging subsystem may be used forregistering and/or fusing the multiple data sets obtained by the varioussubsystems of the present invention, by methods described for instancein “Method for registering multiple data sets,” U.S. patent applicationSer. No. 12/418,841, which is incorporated herein by reference. As setforth in application Ser. No. 12/418,841, wavefront aberrometry may befused with corneal topography, optical coherence tomography andwavefront, optical coherence tomography and topography, pachymetry andwavefront, etc. For instance, with image recognition techniques it ispossible to find the position and extent of various features in animage. Regarding iris registration images, features that are availableinclude the position, size and shape of the pupil, the position, sizeand shape of the outer iris boundary (OIB), salient iris features(landmarks) and other features as are determined to be needed. Usingthese techniques, both patient movement between measurements (and/orduring a measurement sequence) can be identified, as well as changes inthe eye itself (including those induced by the measurement, such aschanges in the size of the pupil, changes in pupil location, etc.).

In many embodiments, an optical measurement system according the presentincludes a target fixation system 50 (FIG. 10), and an assembly 100shown in FIGS. 11A and 11B includes fixation target subsystem 180 whichincludes optics 186 and a fixation target 182 for the patient to view.Fixation target subsystem 180 is used to control the patient'saccommodation for wavefront aberrometry measurements, as describedabove, and because it is often desired to measure the refraction andwavefront aberrations when eye 100 is focused at its far point (e.g.,because LASIK treatments are primarily based on this). In the fixationtarget subsystem 180, a projection of target 182, for instance thetarget shown in FIG. 7A is projected onto the eye 101 of the patient,where target 182 is formed as a video which is shown on a video displaydevice which is included in fixation target subsystem 180, wherein thevideo includes Bokeh compensation, as discussed above.

In operation, light originates from the light source 152 or,alternatively, from video target backlight 182 and lens 186. Lens 185collects the light and forms an aerial image T2. This aerial image isthe one that the patient views. The patient focus is maintained onaerial image 182 during measurement so as to maintain the eye in a fixedfocal position.

The operating sequence the optical measurement system and methods of thepresent is not particularly limited. A scan of the patient's eye maycomprise one or more of a wavefront aberrometry measurement of apatient's eye utilizing the wavefront aberrometry subsystem, a cornealtopography measurement of a patient's eye and an OCT scan of thepatient's eye using the OCT subsystem, wherein the OCT scan includes ascan at each or one or more locations within the eye of the patient.These locations of the OCT scan may correspond to the location of thecornea, the location of the anterior portion of the lens, the locationof the posterior portion of the lens and the location of the retina. Ina preferred embodiment, the operating sequence includes each of awavefront aberrometry measurement, a corneal topography measurement andan OCT scan, wherein the OCT scan is taken at least at the retina, thecornea and one of anterior portion of the patient's lens. An iris imagemay be taken simultaneously with or sequentially with an each ofmeasurements taken with wavefront aberrometry subsystem the cornealtopography subsystem and the OCT subsystem, including an iris image takesimultaneously with or sequentially with the location of each OCT scan.This results in improved accuracy in the 3-dimensional modeling of thepatient's eye by permitting the various data sets to be fused and mergedinto a 3-dimensional model.

FIG. 16 shows one embodiment of an operating sequence and method inwhich wavefront aberrometry measurements, corneal topographymeasurements and OCT measurements are all taken. The optical measurementapparatus, including the method of FIG. 16 may be used preoperatively,intra-operatively and/or postoperatively. In the method of FIG. 16, astep 801 comprises aligning the optical measurement system to the eye ofthe patent. A step 805 comprises activating the fixation targetsubsystem for patient fixation on the fixation target. A step 810comprises activating the wavefront aberrometer subsystem such that thewavefront aberrometer light source 810 is activated and the eyerefraction is measured via the wavefront sensor. A step 815 comprisesactivating the fixation target system to move the target to an optimumposition and activate the wavefront aberrometer subsystem such that thewavefront aberrometer light source 152 is activated and the eyerefraction is measured via the wavefront sensor 155. Beneficially, Bokehcompensation, as described above, may be applied to the fixation targetin step 815. A step 820 comprises obtaining an iris image using IrisImaging Subsystem 40 while infrared light source 152 is operating. Astep 825 comprises operating the z-scan device to set OCT scan locationat or near cornea, and performing an OCT Scan with the OCT Subsystem. Astep 830 comprises operating the z-scan device to set the OCT locationat a location at or near the lens anterior and performing an OCT Scanwith the OCT Subsystem. A step 835 comprises operating the z-scan deviceto set the OCT location at a location at or near the lens posterior andperforming an OCT Scan with the OCT Subsystem. A step 840 comprisesoperating the X-scan device and Y-scan device so no light from OCTreaches detector 141. A step 845 comprises obtaining an iris image usingthe Iris Imaging Subsystem while the infrared light source 152 flashes.A step 850 comprises obtaining an iris image using the Iris ImagingSubsystem while the light sources 120 and Helmholz source flash. A step855 comprises measuring the corneal topography with the CornealTopography Subsystem. A step 855 comprises operating the z-scan deviceto set the OCT location at a location at or near the retina andperforming an OCT Scan with the OCT Subsystem. A step 860 comprisesoperating the X-scan device and Y-scan device so no light from OCTreaches detector 141. An optional step 865 comprises measuring cornealtopography with Corneal Topography Subsystem, which may provide for animproved 3D model of the patient eye. An optional step 870 comprisesobtaining an iris image using Iris Imaging Subsystem (for 3D model).

The optical measurement instrument 1 and the optical measurementsobtained therewith may be used pre-operatively, i.e. before a cataractsurgery or other surgical procedure, for, e.g., eye biometry and othermeasurements, diagnostics and surgical planning. Surgical planning mayinclude one or more predictive models. In the one or more predictivemodels, one or more characteristics of the postoperative condition ofthe patient's eye or vision is modeled based on one or more selectedfrom the group consisting of pre-operative measurements obtained fromthe optical measurement instrument 1, a contemplated surgicalintervention, and on or more algorithms or models stored in the memoryof the optical measurement system 1 and executed by the processor. Thecontemplated surgical intervention may include the selection of an IOLfor placement, the selection of an IOL characteristic, the nature ortype of incision to be used during surgery (e.g., relaxation incision),or one or more post-operative vision characteristics requested by thepatient.

The optical measurement instrument 1 and the optical measurementsobtained therewith may be used intra-operatively, i.e., during acataract surgery or other surgical procedure, for, e.g., intraoperativeeye diagnostics, determining IOL placement and position, surgicalplanning, and control/or of a laser surgical system. For instance, inthe case of laser cataract surgical procedure, any measurement dataobtained preoperatively by the optical measurement instrument may betransferred to a memory associated with a cataract laser surgical systemfor use before, during or after either the placement of a capsulotomy,fragmentation or a patient's lens or IOL placement during the cataractsurgery. In some embodiments, measurements using optical measurementinstrument 1 may be taken during the surgical procedure to determinewhether the IOL is properly placed in the patient's eye. In this regard,conditions measured during the surgical procedure may be compared to apredicted condition of the patient's eye based on pre-operativemeasurements, and a difference between the predicted condition and theactual measured condition may be used to undertake additional orcorrective actions during the cataract surgery or other surgicalprocedure.

The optical measurement instrument 1 and the optical measurementsobtained therewith may be used postoperatively, i.e., after a cataractsurgery or other surgical procedure, for, e.g., post-operativemeasurement, postoperative eye diagnostics, postoperative IOL placementand position determinations, and corrective treatment planning ifnecessary. The postoperative testing may occur sufficiently after thesurgery that the patient's eye has had sufficient time to heal and thepatient's vision has achieved a stable, postsurgical state. Apostoperative condition may be compared to one or more predictedcondition performed pre-operatively, and a difference between thepreoperatively predicted condition and the postoperatively measuredcondition may be used to plan additional or corrective actions duringthe cataract surgery or other surgical procedure.

The optical measurement instrument 1, including the corneal topographysubsystem, the OCT subsystem and the wavefront aberrometry subsystem,utilizing a suitable operating sequence as disclosed herein, is operableto measure one, more than one or all of the following: ocular biometryinformation, anterior corneal surface information, posterior cornealsurface information, anterior lens surface information, posterior lenssurface information, lens tilt information and lens positioninformation. In some embodiments, the ocular biometry information mayinclude a plurality of central corneal thicknesses (CCT), an anteriorchamber depth (ACT), a pupil diameter (PD), a white to white distance(WTW), a lens thickness (LT), an axial length (AL) and a retinal layerthickness. This measurement data may be stored in memory 62 associatedwith controller 60. The plurality of characteristics may be measuredpreoperatively, and where appropriate, intra-operatively, andpostoperatively.

In some embodiments, memory 62 associated with controller 60 may storeintraocular lens (IOL) model data for a plurality of IOL models, each ofthe IOL models having associated with it a plurality of predeterminedparameters selected from the group consisting of dioptic power,refractive index, asphericity, toricity, haptic angulation and lensfilter. The IOL data may be used by one or more processors of opticalmeasurement instrument 1, in conjunction with measurement data of asubject's eye obtained by optical measurement instrument 1, for cataractdiagnostics or cataract treatment planning, which may include specifyingand/or selecting a particular IOL for a subject's eye. For example, oneor more processors of optical measurement instrument 1 may execute analgorithm which includes: accessing the plurality of IOL models storedin, and for each of the IOL models: (1) modeling the subject's eye withan intraocular lens corresponding to the IOL model and the measuredcharacteristics of the subject's eye; (2) simulating the subject's eyebased on the plurality of IOL predetermined parameters and the predictedIOL position; (3) performing one of a ray tracing and a powercalculation based on said model of the subject's eye; and (4) selectingan IOL for the subject's eye from the plurality of IOL modelscorresponding to the optimized IOL based on a predetermined criteria.

In some embodiments, one or more processors of optical measurementinstrument 1 may execute an algorithm comprising: determining a desiredpostoperative condition of the subject's eye; empirically calculating apost-operative condition of the eye based at least partially on themeasured eye characteristics; and predictively estimating, in accordancewith an output of said empirically calculating and the eyecharacteristics, at least one parameter of an intraocular lens forimplantation into the subject's eye to obtain the desired postoperativecondition.

In many embodiments, the eye imaging and diagnostic system furthercomprises a memory operable to store Intraocular Lens (“IOL”) Data, theIOL data including a plurality of dioptic power, anterior and posteriorradius, IOL thickness, refractive index, asphericity, toricity,echelette features, haptic angulation and lens filter.

In many embodiments, the eye imaging and diagnostic system furthercomprises a memory operable to store intraocular lens (“IOL”) model datafor a plurality of IOL models, IOL model having associated with aplurality of predetermined parameters selected from the group consistingof dioptic power, anterior and posterior radius, IOL thickness,refractive index, asphericity, toricity, echelette features, hapticangulation and lens filter.

An improved system for selecting an intraocular lens (IOL) forimplantation, comprises: a memory operable to store data acquired fromeach of the corneal topography subsystem, the wavefront sensor subsystemand the Optical Coherence Tomography subsystem, wherein the stored dataincludes a plurality of ocular biometry information, anterior cornealsurface information, posterior corneal surface information, anteriorlens surface information, and posterior lens surface information, lenstilt information and lens position information; the memory furtheroperable to store intraocular lens (“IOL”) model data for a plurality ofIOL models, IOL model having associated with it a plurality ofpredetermined parameters selected from the group consisting of diopticpower, anterior and posterior radius, IOL thickness, refractive index,asphericity, toricity, echelette features, haptic angulation and lensfilter; and a processor coupled to the memory, the processor derivingthe treatment of the eye of the patient applying, for each of theplurality of identified IOL Model, to: (1) predict a position of one ofthe identified IOL Models when implanted in the subject eye, based onthe plurality of characteristics; (2) simulate the subject eye based onthe plurality of IOL predetermined parameters and the predicted IOLposition; (3) perform one or more of ray tracing and a IOL sphericalequivalent (SE) and cylinder (C) power calculation, as well asoptionally, to determine the optimum IOL orientation based on said eyemodel; and (4) propose one IOL power for one or more IOL models from theplurality of IOLs corresponding to the optimized IOL(s) based onpredetermined criteria; and (5) show the simulated optical qualityand/or visual performance provided by each of the proposed IOL modelsfor distance and/or for any other vergence.

A method of selecting an intraocular lens (IOL) to be implanted in asubject's eye, comprising: measuring a plurality of eye characteristicscomprising ocular biometry information, anterior corneal surfaceinformation, posterior corneal surface information, anterior lenssurface information, and posterior lens surface information, lens tiltinformation and lens position information; and for each of IntraocularLens (“IOL”) model having associated with it a plurality ofpredetermined parameters selected from the group consisting of diopticpower, refractive index, anterior and posterior radius, IOL thickness,asphericity, toricity, echelette design, haptic angulation and lensfilter: (1) modeling the subject eye with the intraocular lens; (2)simulating the subject eye based on the plurality of IOL predeterminedparameters and the predicted IOL position; (3) performing a ray tracingand a IOL spherical equivalent (SE) and cylinder (C) power calculation,as well as determine the optimum IOL orientation based on said eyemodel; and (4) proposing one IOL power for one or more IOL models fromthe plurality of IOLs corresponding to the optimized IOL(s) based onpredetermined criteria; and optionally (5) show the simulated opticalquality and/or visual performance provided by each of the proposed IOLmodels for distance and/or for any other vergence.

A tangible computer-readable storage device storing computerinstructions which, when read by a computer, cause the computer toperform a method comprising: receiving a plurality of eyecharacteristics comprising ocular biometry information, anterior cornealsurface information, posterior corneal surface information, anteriorlens surface information, and posterior lens surface information, lenstilt information and lens position information; for each of IntraocularLens (“IOL”) model having associated with it a plurality ofpredetermined parameters selected from the group consisting of diopticpower, refractive index, anterior and posterior radius, IOL thickness,asphericity, toricity, echelette design, haptic angulation and lensfilter: (1) simulating a geometry of the subject eye with each of theplurality of intraocular lenses (IOL) implanted, in accordance with theplurality of eye characteristics; (2) performing a ray tracing and a IOLspherical equivalent (SE) and cylinder (C) power calculation, as well asoptionally determining the optimum IOL orientation based on said eyemodel; (3) proposing one IOL power for one or more IOL models from theplurality of IOLs corresponding to the optimized IOL(s) based onpredetermined criteria; and optionally (4) showing the simulated opticalquality and/or visual performance provided by each of the proposed IOLmodels for distance and/or for any other vergence.

A method of predicting the intraocular lens position comprising:determining a plurality of eye characteristics before cataract surgery,comprising ocular biometry information, anterior corneal surfaceinformation, posterior corneal surface information, anterior lenssurface information, and posterior lens surface information, lens tiltinformation and lens position information; determining a plurality ofeye characteristics after cataract surgery, comprising ocular biometryinformation, anterior corneal surface information, posterior cornealsurface information, anterior lens surface information, and posteriorlens surface information, lens tilt information and lens positioninformation; calculating or measuring, based on a mathematicalrelationship, a distance from the apex to a plane of the intraocularlens after an ocular surgical procedure; calculating an optical power ofthe intraocular lens suitable for providing a predetermined refractiveoutcome; wherein a mathematical relationship is found between thepreoperative and postoperative eye characteristics that accuratelypredict the measured distance from the apex to the plane where theintraocular lens is.

An improved system for planning a refractive treatment of an eye of apatient, the system comprising: a memory operable to store eyemeasurement data comprising ocular biometry information, anteriorcorneal surface information, posterior corneal surface information,anterior lens surface information, and posterior lens surfaceinformation, lens tilt information and lens position information; aprocessor coupled to the memory, the processor deriving the treatment ofthe eye of the patient applying an effective treatment transferfunction, wherein the effective treatment transfer function is derivedfrom, for each of a plurality of prior eye treatments, a correlationbetween a pre-treatment vector characterizing the eye measurement databefore treatment, and a post-treatment vector characterizingpost-treatment eye measurement data of the associated eye; an outputcoupled to the processor so as to transmit the treatment to facilitateimproving refraction of the eye of the patient. The processor maycomprise tangible media embodying machine readable instructions forimplementing the derivation of the treatment.

A method for planning a refractive treatment of an eye of a patient,comprises: measuring a plurality of ocular biometry information,anterior corneal surface information, posterior corneal surfaceinformation, anterior lens surface information, and posterior lenssurface information, lens tilt information and lens positioninformation.

A method of customizing at least one parameter of an intraocular lens,comprises: measuring a plurality of eye characteristics comprisingocular biometry information, anterior corneal surface information,posterior corneal surface information, anterior lens surfaceinformation, and posterior lens surface information, lens tiltinformation and lens position information; determining a desiredpostoperative condition of the eye; empirically calculating apost-operative condition of the eye based at least partially on themeasured eye characteristics; and predictively estimating, in accordancewith an output of said empirically calculating and the eyecharacteristics, the at least one parameter of the intraocular lens toobtain the desired postoperative condition.

A method of adjusting the refractive power in an eye of a patient whohas undergone cataract surgery comprises: measuring a plurality ofpost-operative eye characteristics in an eye of a patient who haspreviously undergone cataract surgery, the eye characteristicscomprising ocular biometry information, anterior corneal surfaceinformation, posterior corneal surface information, anterior lenssurface information, and posterior lens surface information, lens tiltinformation and lens position information; identifying a plurality ofcorrective procedure based at least partially on one of (1) a comparisonof at least one measured pre-operative eye characteristic and thecorresponding measured post-operative eye characteristic; and (2) acomparison of at least one predicted post-operative eye characteristicand the corresponding measured post-operative eye characteristic; foreach of a plurality of corrective procedures: modeling the subject eyewith the corrective procedure; modeling the subject eye based on thecorrective procedure; performing one of a ray tracing and a powercalculation based on said eye model; and selecting a correctiveprocedure from the plurality of IOL models corresponding to theoptimized IOL based on a predetermined criteria.

In some embodiments, the system further comprises a processor configuredto execute an algorithm. The algorithm comprises, for each of the IOLmodels: (1) modeling the subject's eye with an intraocular lenscorresponding to the IOL model and the measured characteristics of thesubject's eye; (2) simulating the subject's eye based on the pluralityof IOL predetermined parameters and the predicted IOL position; (3)performing one of a ray tracing and a power calculation based on saidmodel of the subject's eye; and (4) selecting an IOL from the pluralityof IOL models corresponding to the optimized IOL based on apredetermined criteria.

This summary and the following detailed description are merelyexemplary, illustrative, and explanatory, and are not intended to limit,but to provide further explanation of the invention as claimed.Additional features and advantages of the invention will be set forth inthe descriptions that follow, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription, claims and the appended drawings.

All patents and patent applications cited here are hereby incorporatedby reference hereby reference in their entirety.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated here or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values here are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described here can be performed in any suitableorder unless otherwise indicated here or otherwise clearly contradictedby context. The use of any and all examples, or exemplary language(e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention, and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

While certain illustrated embodiments of this disclosure have been shownand described in an exemplary form with a certain degree ofparticularity, those skilled in the art will understand that theembodiments are provided by way of example only, and that variousvariations can be made and remain within the concept without departingfrom the spirit or scope of the invention. Such variations would becomeclear to one of ordinary skill in the art after inspection of thespecification, drawings and claims herein. Thus, it is intended thatthis disclosure cover all modifications, alternative constructions,changes, substitutions, variations, as well as the combinations andarrangements of parts, structures, and steps that come within the spiritand scope of the invention as generally expressed by the followingclaims and their equivalents.

We claim:
 1. A system, comprising: a wavefront aberrometer configured tomeasure a refraction of an eye; at least one processor; a video displaydevice; and an optical system disposed in an optical path between thevideo display device and the eye, wherein the video display devicepresents a fixation target to the eye to cause the eye to accommodateduring a process of measuring the refraction of the eye, and wherein theat least one processor is configured to dynamically change the fixationtarget on the video display device to compensate for Bokeh of thefixation target as the video display device is moved from a firstposition, where the fixation target draws a focus of the eye to near itsfar point, to a second position which is further away from the eye thanthe first position.
 2. The system of claim 1, wherein the at least oneprocessor is configured to move the fixation target with respect to theeye.
 3. The system of claim 2, further comprising a first movable stage,wherein the first movable stage is movable with respect to the eye undercontrol of the at least one processor.
 4. The system of claim 3, furthercomprising a second movable stage disposed on the first movable stage,wherein the video display device is disposed on the second movablestage, wherein the second movable stage is independently movable withrespect to the first movable stage and with respect to the eye, undercontrol of the at least one processor.
 5. The system of claim 1, whereina size of the fixation target on the video display device remainssubstantially constant as the video display device is moved further awayfrom the eye.
 6. The system of claim 1, wherein the fixation targetcomprises a cross formed by two lines, including a horizontal line and avertical line, intersecting at an intersection, and wherein theprocessor is configured to control the video display device todynamically reduce a thickness of the horizontal line and a thickness ofthe vertical line as the video display device is moved further away fromthe eye.
 7. The system of claim 1, wherein the fixation target comprisesa cross formed by two lines, including a horizontal line and a verticalline, intersecting at an intersection, and wherein the processor isconfigured to control the video display device to cause each of thehorizontal line and the vertical line to have a dynamically increasingtaper down to the intersection as the video display device is movedfurther away from the eye.
 8. The system of claim 1, wherein thefixation target comprises a cross formed by two lines, including ahorizontal line and a vertical line, intersecting at an intersection,and wherein the processor is configured to control the video displaydevice to dynamically decrease an intensity of the cross at a regionabout the intersection as the video display device is moved further awayfrom the eye.
 9. A method, comprising: providing an arrangementcomprising: a wavefront aberrometer configured to measure a refractionof an eye; at least one processor; a video display device; and anoptical system disposed in an optical path between the video displaydevice and the eye; the video display device presenting a fixationtarget to the eye to cause the eye to accommodate during a process ofmeasuring the refraction of the eye; moving the video display devicewith respect to the eye to a first position where the fixation targetdraws a focus of the eye to near its far point; moving the video displaydevice with respect to the eye to a second position where the videodisplay device is moved away from the eye by an additional amount; anddynamically changing the fixation target on the video display device tocompensate for Bokeh of the fixation target as the video display deviceis moved away from the eye by the additional amount.
 10. The method ofclaim 9, wherein dynamically changing the fixation target on the videodisplay device to compensate for Bokeh of the fixation target as thefixation target is moved away from the eye by the additional amountcomprises playing a movie on the video target.
 11. The method of claim10, further comprising: modeling effects of the optical system andaberrations of the eye to determine a series of model fogged images ofthe fixation target on a retina of the eye as a function of a distancefrom the video display device to the eye; analyzing the model foggedimages to identify features in the model fogged images which areinconsistent with how the fixation target would appear as the videodisplay device moved more distant from the eye while the fixation targetwas viewed directly by the eye; and creating the movie by performinginverse operations on the fixation target according to the identifiedfeatures in the model fogged images to compensate for the identifiedfeatures as the function of the distance from the video display deviceto the eye.
 12. The method of claim 11, wherein the fixation targetcomprises a cross formed by two lines, including a horizontal line and avertical line, intersecting at an intersection, and wherein the moviedynamically reduces a thickness of the horizontal line and a thicknessof the vertical line as the video display device is moved further awayfrom the eye.
 13. The method of claim 11, wherein the fixation targetcomprises a cross formed by two lines, including a horizontal line and avertical line, intersecting at an intersection, and wherein the moviecauses each of the horizontal line and the vertical line to have adynamically increasing taper down to the intersection as the videodisplay device is moved further away from the eye.
 14. The method ofclaim 11, wherein the fixation target comprises a cross formed by twolines, including a horizontal line and a vertical line, intersecting atan intersection, and wherein the movie dynamically decreases anintensity of the cross at a region about the intersection as the videodisplay device is moved further away from the eye.
 15. The method ofclaim 9, further comprising measuring a refraction of the eye with thefirst movable stage at the first stage position and the second stage atthe second stage position.
 16. The method of claim 10, comprisingmeasuring the refraction of the eye with a wavefront aberrometer havinga wavefront sensor and a telescope, wherein a first lens of thetelescope is disposed on the first stage and a second lens of thetelescope is not disposed on the first stage or the second stage.
 17. Asystem, comprising: at least one processor; a first movable stage,wherein the first movable stage is movable under control of the at leastone processor with respect to an eye of a subject; a video displaydevice configured to move with the first movable stage; and an opticalsystem disposed in an optical path between the video display device andthe eye, wherein the video display device is configured to play a movieof a fixation target to the eye to cause the eye to accommodate, andwherein the movie dynamically changes an appearance of the fixationtarget on the video display device to compensate for Bokeh of thefixation target as the first movable stage moves the video displaydevice from a first position, where the fixation target draws a focus ofthe eye to near its far point, to a second position further away fromthe eye than the first position.
 18. The system of claim 17, furthercomprising a second movable stage disposed on the first movable stage,wherein the video display device is disposed on the second movablestage, wherein the second movable stage is independently movable withrespect to the first movable stage and with respect to the eye, undercontrol of the at least one processor.
 19. The system of claim 17,wherein the fixation target comprises a cross formed by two lines,including a horizontal line and a vertical line, intersecting at anintersection, and wherein the processor is configured to control thevideo display device to dynamically reduce a thickness of the horizontalline and a thickness of the vertical line as the video display device ismoved further away from the eye.
 20. The system of claim 17, wherein thefixation target comprises a cross formed by two lines, including ahorizontal line and a vertical line, intersecting at an intersection,and wherein the processor is configured to control the video displaydevice to cause each of the horizontal line and the vertical line tohave a dynamically increasing taper down to the intersection as thevideo display device is moved further away from the eye.